mwave offers the refurbished TRENDnet Wireless USB 2.0 Adapter, model no. TEW-644UB, with a $3 mwave Gift Coupon for $12.99 with free shipping. Assuming you use the credit, that's the lowest total price we've seen for this adapter and a current low by $10. This adapter is purported to provide coverage of up to 164 feet indoors and 328 feet outdoors.

A 6-month warranty applies, although it's unclear who backs it.